GIFT  OF 


UNIVERSITY  OF  CALIFORNIA 

COLLEGE  OF  AGRICULTURE 

BERKELEY 


AGRICULTURAL  EXPERIMENT  STATION 


BENJ.   IDE    WHEELER,    PRESIDENT 

THOMAS  FORSYTH   HUNT,   DEAN  Al 

H.  E.  VAN   NORMAN,  VlCE-DlRECTO 

UNIVERSITY  FARM  S 


CIRCULAR  No.  108 

OCTOBER,    1913 


GRAPE  JUICE, 


By  F.  T.  BIOLETTI. 


This  short  account  of  methods  of  preserving  unfermented  grape  juice 
is  prepared  in  answer  to  the  very  numerous  inquiries  received  at  the 
Station  on  this  subject.  No  attempt  is  made  to  explain  in  detail  all 
the  methods  and  appliances  necessary  for  preparing  grape  juice  on  a 
commercial  scale.  Only  the  fundamental  processes  and  principles  are 
discussed  together  with  enough  detail  to  enable  anybody  to  devise 
means  to  conserve  small  quantities  for  domestic  use,  or  to  judge  of  the 
efficacy  of  industrial  methods  or  installations. 

OUTLINE  OF  PROCESS. 

Gathering  and  Care  of  the  Grapes. 

Extraction  of  Juice. 

Stemming,  Crushing,  Draining,  Pressing. 

Preliminary  Clearing  or  Defecation. 

Sulfiting,,  Settling,  Racking,  (Fining?). 

Final  Clearing. 

Pasteurizing,  Settling,  Addition  of  Acid,   (Fining?),  Filtering. 

Conservation. 

Bottling,  Corking,  Sterilizing. 

The  various  steps  in  the  process  have  two  objects — to  preserve  the 
juice  from  spoiling  and  to  make  it  permanently  clear.  Both  objects 
should  be  accomplished  with  as  little  change  of  the  flavor  of  the  fresh 
juice  as  possible.  If  the  juice  is  for  home  consumption  and  perfect 
clearness  is  not  necessary,  the  process  can  be  shortened  and  simplified. 
It  can  be  still  further  simplified  by  adopting  the  methods  used  for 
ordinary  preserving  of  fruit.  In  the  last  case,  the  fresh  flavor  of  the 
juice  is  destroyed  and  it  is  not  relished  by  most  people. 

1.  Gathering  the  Grapes.  Only  good,  sound  grapes,  carefully  gath- 
ered in  a  cleanly  way  should  be  used.  It  is  best  to  gather  them  in  the 
morning  while  cool,  or  to  leave  them  all  night  exposed  to  the  open  sky 
to  cool  off  before  crushing.  ^  ." 


2  

2.  Crushing  and  Stemming.     The  cool  grapes  should  be  thoroughly 
broken  and  the  pulp  crushed  by  passing  between  rollers  or  by  some 
similar  method.     The  seeds  should  not  be  broken  nor  the  skins  macer- 
ated too  much  or  the  juice  will  be  harsh,  astringent  and  difficult  to  clear. 
On  the  other  hand,  if  the  pulp  is  not  well  broken  up,  the  yield  of  juice 
will  be  low. 

3.  Separation  of  Juice.     A  considerable  portion  of  the  juice  will 
run  off  if  the  crushed  grapes  are  allowed  to  stand  for  a  few  hours  in  a 
drainage  cage.    This  cage  may  be  the  press  basket,  a  box  furnished  with 
a  false  bottom  of  slats,  an  open  fermenting  vat  with  a  good  strainer 
at  the  bottom,  or  some  similar  device. 

After  draining,  the  crushed  grapes  are  pressed  to  extract  more  of  the 
juice.  A  cider  press  or  any  of  the  presses  used  in  wineries  may  be  used 
for  this  purpose,  with  the  exception  of  the  ordinary  continuous  presses, 
which  are  not  advisable,  as  they  macerate  the  grapes  too  much  and  pro- 
duce a  turbid  juice  that  is  difficult  to  clear.  The  fresh  grapes  have  a 
tendency  to  squirt  out  through  the  interstices  of  the  press,  especially  if 
the  stems  have  been  removed,  as  is  generally  done  directly  before  or 
after  crushing.  This  can  be  prevented  by  lining  the  bottom  and  sides 
of  the  press  basket  with  grape  stems  as  it  is  being  filled.  Clean  straw 
is  sometimes  used  for  the  same  purpose. 

For  the  best  results,  the  pressing  should  be  slow  and  gradual.  A 
lever  press  gives  excellent  results  on  a  small  scale.  The  pressed 
"pomace"  may  be  forked  over  and  pressed  a  second  or  third  time. 
If  any  water  is  to  be  used,  it  is  best  sprinkled  on  the  turned  pomace 
before  the  second  and  third  pressings. 

4.  Defecation.     The  free  run  and  the  press  juice  are  more  or  less 
cloudy,  owing  to  floating  particles  of  skin,  pulp,  etc.     If  the  grapes  are 
clean  and  sound,  this  may  not  injure  the  flavor  noticeably  and  for  home 
use  it  may  be  bottled  immediately  and  sterilized  as  explained  later. 
It  is  very  much  improved,  however,  in  appearance  and  somewhat  in 
flavor,  by  a  preliminary  "defecation"  or  clearing.     This  is  obtained 
by  allowing  the  juice  to  remain  undisturbed  in  casks  or  open  vats 
until  the  grosser  particles  settle  and  form  a  sediment. 

This  defecation  requires  from  twelve  to  forty-eight  hours,  usually 
about  twenty-four  to  thirty-six.  It  will  therefore  be  from  two  to  three 
days  after  the  crushing  of  the  grapes  before  the  clear  juice  is  obtained. 
During  this  time,  there  is  danger  of  fermentation  starting,  which  would 
spoil  the  juice.  If  the  grapes  are  cold  when  crushed  and  the  weather 
remains  cool,  the  juice  can  sometimes  be  cleared  successfully  in  this 
way.  It  is  usually  necessary,  however,  to  take  measures  to  prevent 
fermentation.  There  are  two  methods  of  doing  this.  One  is  to  put  the 
jnice  ia+o  a  ?o':d '.storage  room  below  50°  F.  If  the  grapes  are  in  poor 


condition  or  the  juice  warm,  it  may  be  necessary  to  have  the  room  much 
colder  than  this.  The  other  method  is  to  paralyze,  temporarily,  the 
fermentation  organisms  with  sulfurious  acid. 

The  best  way  of  applying  the  latter  method  is  the  use  of  potassium- 
metabisulfit.  This  is  used  in  the  form  of  a  ten  per  cent  solution  in 
water  at  the  rate  of  from  5  ounces  to  10  ounces  of  the  sulfit  to  one  ton  of 
grapes  or  two  hundred  gallons  of  the  juice.  The  sweeter  and  warmer 
the  juice  the  more  sulfit  is  needed. 

The  best  way  of  applying  the  sulfit  is  to  add  the  solution  gradually 
to  the  crushed  grapes  as  they  fall  from  the  crusher  or  into  the  drainage 
box.  In  this  way,  the  ferments  are  prevented  from  making  even 
a  commencement  of  development  and  a  smaller  quantity  of  sulfit  will 
suffice.  The  use  of  sulfit  must  not  be  considered  as  a  substitute  for 
care  in  handling  and  keeping  the  grapes  cool,  but  only  as  an  additional 
precaution  against  injurious  fermentation.  The  juice  should  be  as  cool 
as  is  practicable,  but  may  be  defecated  perfectly  by  this  means  if  it  does 
not  rise  above  70°  F. 

The  sulfit  must  be  carefully  measured  and  evenly  distributed.  If 
too  much  is  used,  it  will  injure  the  flavor  of  the  juice.  If  too  little,  it 
may  not  accomplish  its  object.  An  excess  of  ten  or  twenty  per  cent 
over  the  amounts  indicated  will  do  little  or  no  harm  and  would  still  be 
several  times  less  than  the  legal  limitations  for  dried  fruits  and  wine. 

Defecation  by  means  of  sulfurous  acid  is  not  only  simpler  but  better 
than  by  means  of  refrigeration.  It  not  only  prevents  injurious  fer- 
mentations more  effectually,  but  it  prevents  undue  oxidation  of  the 
juice  during  the  processes  of  preparation.  Oxidation  is  one  of  the  main 
causes  of  the  loss  of  the  finer  flavors  of  the  fresh  juice.  This  is  not 
prevented  but  rather  increased  by  refrigeration. 

5.  Pasteurization.  The  prevention  of  fermentation  by  means  of  the 
metabisulfit  is  only  temporary  and,  even  in  cold  storage,  fermentation 
will  develop  slowly  unless  the  juice  is  kept  close  to  the  freezing  point. 
The  clear  juice,  therefore,  must  be  separated  from  the  sediment  as  soon 
as  it  has  settled  and  before  even  the  commencement  of  fermentation  has 
occurred.  At  the  end  of  forty-eight  hours,  at  the  latest,  therefore,  it 
should  be  drawn  off.  Even  though  it  still  appears  cloudy,  most  of  the 
gross  sediment  will  have  settled. 

In  many  cases,  it  will  be  nearly  bright,  and,  if  intended  for  domestic 
use,  it  is  best  to  bottle  and  sterilize  it  at  this  point.  However  bright  it 
may  be  at  this  point,  it  is  not  safe  to  bottle  it  for  commercial  use,  as  it 
will  become  cloudy  again  in  bottle.  This  new  cloudiness  is  due  to 
crystallization  and  precipitation ;  that  is,  the  becoming  solid  of  certain 
substances  which  are  at  first  dissolved  in  the  juice.  The  chief  of  these 
substances  is  the  bitartrate  of  potash  or  cream  of  tartar.  These  sub- 
stances precipitate  slowly,  often  requiring  weeks,  or  even  months. 


In  order  to  give  the  substances  time  to  deposit,  the  juice  is  pasteur- 
ized to  kill  the  ferments  which  have  been  only  temporarily  paralyzed 
by  sulfiting  or  refrigeration. 

This  pasteurizing  is  sometimes  applied  to  the  fresh  juice  without 
preliminary  defecation.  This  involves  heating  the  juice  while  it  still 
contains  all  its  gross  sediment.  This  results  in  deterioration  of  flavor, 
difficulty  in  clearing,  and  clogging  of  the  pasteurizer. 

Pasteurizing  is  heating  to  a  degree  and  for  a  time  sufficient  to  kill 
all  ferments  which  are  in  the  juice  and  are  capable  of  injuring  it. 

The  killing  of  the  germs  depends  both  on  the  degree  of  temperature 
reached  and  on  the  time  during  which  this  degree  is  maintained.  A 
momentary  heating  to  175°  F.  will  kill  most  yeasts  and  molds  com- 
monly found  in  grape  juice,  but  at  140°  F.,  some  of  the  resistant  spores 
would  escape.  If  the  must  is  heated  to  140°  F.  and  kept  at  that 
temperature  for  several  hours,  the  effect  would  be  equal  to  175°  F.  for 
a  minute. 

The  lower  the  temperature  of  pasteurization  the  less  the  flavor  of 
the  juice  is  injured.  It  must  be  high  enough,  however,  to  insure  keep- 
ing. In  practice,  with  present  methods,  it  is  necessary  to  heat  at  least 
to  160°  F.  If  the  must  is  sulfited  and  run  hot  into  sterilized  casks  of 
at  least  fifty  gallons  capacity  where  it  will  keep  hot  for  some  hours, 
this  temperature  should  be  sufficient.  If  the  heated  must  cools  rapidly 
as  when  put  in  bottles,  or  if  the  casks  are  imperfectly  sterilized  before 
filling,  a  higher  temperature  will  be  needed.  The  flavor  of  the  juice  is 
not  seriously  injured  below  175°  F.  when  sulfit  is  used. 

For  domestic  purposes,  the  pasteurizing  is  best  done  by  placing  the 
fruit  in  large  fruit  jars  or  demijohns  and  heating  them,  surrounded 
by  water,  in  a  boiler,  as  is  done  in  bottling  fruit.  Two  thermometers 
should  be  used,  one  in  one  of  the  jars,  and  the  other  in  the  water  of 
the  boiler.  The  thermometer  in  the  jar  should  reach  to  the  bottom 
where  the  juice  heats  more  slowly.  The  covers  should  be  placed  loosely 
over  the  jars  and  the  boiler  should  be  covered.  The  water  in  the  boiler 
should  not  exceed  175°  or  180°  F.  and  as  soon  as  the  thermometer  in 
the  jar  indicates  160°  F.  at  the  bottom,  the  fire  should  be  removed, 
the  covers  of  the  jars  screwed  down  tight  and  the  juice  allowed  to  cool 
slowly  in  the  covered  boiler.  These  jars  may  then  be  kept  like  those 
containing  preserved  fruit.  If  placed  upright,  the  solids  eliminated 
will  form  a  sediment  at  the  bottom  and  the  clear  juice  above  may  be 
decanted  for  immediate  consumption,  or  placed  in  bottles,  corked  and 
sterilized  as  described  later. 

On  a  large  scale,  some  form  of  continuous  pasteurizer  is  more  con- 
venient. Some  of  those  used  for  wine  are  suitable,  providing  the  tubes 
or  other  passages  through  which  the  liquid  runs  are  not  too  small. 
Pasteurizers  having  a  great  length  of  narrow  tubing  rapidly  become 


clogged  and  the  viscid  nature  of  the  juice  renders  the  flow  difficult 
and  irregular.  In  pasteurizing  wine,  the  hot  liquid  must  not  come  in 
contact  with  the  air.  With  grape  juice,  this  precaution  is  not  neces- 
sary, especially  if  sulfit  has  been  used.  Too  much  exposure  to  the  air, 
however,  should  be  avoided,  or  the  juice  may  acquire  an  oxidized  taste. 
The  heated  wine  should  pass  directly  from  the  pasteurizer  into 
recently  sterilized  casks.  These  casks  should  be  sterilized  by  means  of 
steam  and  plugged  with  a  wooden  bung  wrapped  with  a  piece  of  cloth 
such  as  ordinary  cotton  sheeting.  Both  bung  and  cloth  should  be 
thoroughly  sterilized  with  boiling  water  and  by  soaking  in  a  two  per 
cent  sulfit  solution.  The  filled  casks  are  then  placed  on  skids,  firmly 
wedged  to  prevent  movement,  and  allowed  to  settle  for  several  weeks. 


D  — 


Air-filtering  Bung  for  Settling  Casks. 
S,  stave  of  cask  ;  J,  surface  of  grape 
juice  ;  B,  wooden  bung  ;  T,  metal  fun- 
nel to  hold  cotton  with  tube  passing 
through  the  bung ;  C,  tightly  packed 
sterilized  cotton  ;  D,  loose  fitting  metal 
cap  of  funnel. 

The  colder  the  room  in  which  they  are  kept,  the  less  danger  there  will 
be  of  fermentation  and  the  more  rapidly  the  juice  will  get  rid  of  its 
cream  tartar. 

The  juice  will  have  to  settle  for  several  weeks  and  unless  the  work 
is  all  done  carefully,  it  runs  the  risk  of  fermenting.  If  the  casks  have 
been  properly  sterilized  and  the  juice  run  in  at  160°  F.,  they  will  be 
completely  free  from  any  germs  which  could  cause  fermentation.  As 
the  juice  cools,  however,  air  will  be  drawn  into  the  cask  by  the  decrease 
of  volume  and,  with  this  air,  some  fermentation  germs  may  enter. 


—  6  — 

This  may  be  prevented  by  use  of  a  device  which  filters  the  air  through 
a  tight  plug  of  sterilized  cotton  as  it  enters.  Such  a  device  is  shown 
in  the  figure. 

This  air-filtering  bung  should  be  put  in  place  of  the  regular  bung 
as  soon  as  the  cask  is  fixed  on  its  skids  and  before  the  juice  has  had 
time  to  cool  in  the  least.  The  best  way,  where  practicable,  is  to 
pasteurize  directly  into  the  casks  after  they  have  been  fixed  in  their 
permanent  resting  places  and  to  insert  the  air-filtering  bung  the  moment 
the  cask  is  full. 

These  air-filtering  bungs  will  be  effective  only  if  carefully  made  and 
properly  handled.  The  bung  hole  of  the  cask  should  be  smooth  and 
regular  and  each  should  have  its  own  bung  fitted  exactly.  The  metal 
tube  through  the  bung  should  fit  close  so  that  no  air  will  pass  between 
it  and  the  Avood.  If  it  is  threaded  so  as  to  screw  into  the  bung  it  will 
make  an  air  tight  joint. 

Before  using,  both  filtering  funnel  and  bung  should  be  sterilized. 

The  funnels  are  first  filled  with  clean  surgeon's  cotton,  packed  fairly 
tight  and  the  loose  metal  caps  put  in  place.  They  are  then  rolled 
in  pieces  of  manila  paper  kept  in  place  by  folding  over  the  ends.  The 
wrapped  funnels  are  then  heated  for  an  hour  in  an  oven  hot  enough 
to  just  slightly  char  the  paper.  A  number  of  wrapped  funnels  may 
be  sterilized  in  a  metal  box  and  kept  in  this  box  until  needed. 

The  bungs  are  sterilized  by  dipping  in  boiling  water  and  then  soak- 
ing until  needed  in  a  2  per  cent  solution  of  sulfit. 

If  the  funnels  and  bungs  are  carefully  handled,  they  can  be  inserted 
into  the  casks  without  danger  of  contamination.  As  soon  as  a  bung  is 
inserted  into  a  filled  cask,  it  is  tapped  in  firm  and  the  cask  immedi- 
ately rolled  a  little  on  one  side.  The  cask  should  be  rolled  over 
sufficiently  to  immerse  the  lower  end  of  the  bung  in  the  hot  juice  but 
not  so  far  that  there  is  danger  of  wetting  the  cotton  in  the  funnel. 

With  all  these  precautions,  a  cask  of  juice  may  occasionally  ferment. 
In  such  cases,  the  juice  can  be  used  for  vinegar.  With  intelligent 
care,  few  or  none  of  them  should  spoil  in  this  way.  The  air-filtering 
bung  acts  as  a  safety  valve  for  the  occasional  cask  which  ferments  and 
which  without  this  outlet  might  blow  out  a  head. 

6.  Final  Clearing.  A  few  weeks  of  settling,  after  pasteurizing, 
will  sometimes  render  the  juice  perfectly  bright.  In  this  case,  the 
permanency  of  the  brightness  should  be  tested.  This  may  be  done  by 
heating  a  corked  bottle  of  the  clear  juice  to  160°  and  then  allowing  it 
to  stand  for  several  days  in  a  cool  place.  If  the  juice  remains  clear,  it 
may  be  bottled.  If  it  becomes  cloudy,  it  should  be  allowed  to  stand 
several  weeks  longer. 

In  some  cases  the  juice  will  not  become  clear  even  after  prolonged 
settling.  It  is  then  necessary  to  filter  it  before  bottling.  It  should 


be  tested  by  filtering  a  few  bottles,  heating  and  allowing  to  stand  as 
explained  above  before  bottling  the  whole  quantity. 

In  nearly  all  cases,  even  when  the  brightness  appears  permanent  by 
these  tests  and  the  juice  is  put  in  the  bottles  clear,  there  will  be  a 
further  deposit  with  time.  This  should  be  very  slight,  however,  and 
should  consist  only  of  fine  crystals  of  cream  of  tartar.  The  formation 
of  these  crystals  in  the  bottle  will  be  prevented  if  a  small  quantity  of 
citric  acid  is  added  to  the  juice  before  filtering.  The  addition  of  this 
acid  is  also  nearly  always  advisable  to  improve  the  flavor  of  the  juice, 
which  with  ripe  vinifera  grapes  tends  to  be  lacking  in  acidity.  Tartaric 
acid  will  improve  the  flavor  in  the  same  way  but  will  not  prevent  the 
formation  of  crystals.  From  one  to  two  pounds  of  citric  acid  to  a 
hundred  gallons  of  juice  is  all  that  is  needed. 

7.  Sterilizing.     The  clear  filtered  juice  should  pass  directly  into 
bottles  which  should  be  corked  and  sterilized  without  delay. 

The  bottles  should  be  carefully  cleaned  and  sterilized  with  boiling 
water  before  filling.  It  is  even  more  important  that  the  corks  should 
be  thoroughly  sterilized.  The  sterilization  of  the  corks  is  more  difficult 
as  resistant  mold  spores  may  be  lodged  in  the  crevices.  It  can  be 
accomplished  by  immersing  the  corks  for  five  nmmtes  in  boiling  water 
to  which  has  been  added  1  per  cent  of  copper  sulfate.  The  corks  should 
then  be  kept  in  2  per  cent  solution  of  metabisulfit  until  used.  Where 
caps  are  used,  there  is  also  danger  of  molding  unless  they  are  sterilized. 
Copper  sulfate  can  not  be  used  in  this  case  as  it  would  attack  the  metal 
of  the  caps.  Boiling  in  pure  water  for  fifteen  minutes  can  be  recom- 
mended. 

As  soon  as  the  clear  juice  is  bottled  and  corked,  it  should  receive  its 
final  sterilization.  This  can  be  done  by  any  means  which  raises  the 
temperature  of  the  juice  in  every  part  of  the  bottle  to  160°  F.  This 
temperature  should  be  maintained  for  at  least  five  minutes.  If  the 
bottles  are  placed  upside  down  or  in  such  a  position  that  the  cork  will 
be  wet  with  the  juice  during  sterilization,  less  trouble  will  be  experi- 
enced from  subsequent  molding  of  the  corks. 

The  bottles  must  not  be  filled  too  full  or  the  expansion  of  the  juice 
in  heating  will  drive  out  the  cork  or  burst  the  bottle.  An  air  space 
of  about  1|  inches  in  the  neck  is  necessary.  Even  then  the  corks  may 
be  driven  out  by  the  compressed  air,  so  it  is  necessary  to  fasten  them  in 
by  tying  with  string  or  with  some  of  the  devices  made  for  this  purpose. 
When  the  sterilizing  is  done  in  a  closed  sterilizer  or  l  i  autoclav, ' '  fasten- 
ing the  corks  is  not  necessary. 

8.  Fining.     The  clearing  of  the  juice  may  be  much  facilitated  and 
hastened  in  many  cases  by  "fining."     This  consists  in  adding  to  the 
juice  a  minute  quantity  of  a  substance  which  will  coagulate  and  settle 
in  the  liquid*,  carrying  down  with  it  all  the  particles  of  solid  matter 


which  cause  the  cloudiness.  This  fining  can  be  applied  at  the  time  of 
the  first  pasteurization  or  just  before  the  final  filtration  and  bottling. 

In  the  first  case,  just  as  soon  as  the  juice  is  cleared  by  defecation,  it 
should  be  drawn  off,  thoroughly  mixed  with  the  finings  and  pasteurized 
into  the  settling  barrels  immediately.*  In  the  second  case,  the  juice 
from  the  settling  casks  is  drawn  off,  mixed  with  finings  and  pasteurized 
again  into  other  casks.  After  remaining  until  clear,  it  is  bottled 
directly  and  sterilized.  Instead  of  allowing  it  to  settle  after  this 
pasteurization,  it  may  be  passed  while  still  hot  through  a  filter  and 
bottled  directly.  When  this  is  done,  the  juice  often  becomes  cloudy 
again  a  short  time  after  bottling.  If  the  juice  after  fining  and  heating 
is  allowed  to  stand  for  a  few  hours  it  can  often  be  made  permanently 
clean  by  filtering. 

The  usual  method  is  to  fine  the  juice  after  settling  for  several  months. 
In  this  case,  an  extra  heating  is  necessary  just  before  bottling.  If  the 
fining  is  done  before  settling  this  extra  heating  is  unnecessary. 

9.  Materials  Used  for  Fining.  The  materials  used  in  fining  wine  can 
be  used  for  grape  juice.  The  amounts  used,  however,  will  differ,  owing 
to  the  greater  cloudiness  of  the  juice  and  the  presence  of  albuminoid 
matters. 

The  commonest  finings  used  for  wine  is  equal  amounts  of  tannin  and 
gelatin.  If  gelatin  is  used  in  grape  juice,  a  much  larger  amount  of 
tannin  will  be  necessary.  Good  results  have  been  obtained  by  the 
use  of  5  ounces  of  tannin  and  2  ounces  of  gelatin  to  100  gallons.  Two 
to  three  ounces  of  tannin  without  the  gelatin  would  probably  be  effec- 
tive in  some  cases  as  the  tannin  would  form  a  precipitate  with  the 
albuminoid  matters  of  the  juice.  The  tannin  should  be  completely 
dissolved  in  a  little  hot  water  and  thoroughly  mixed  with  the  juice 
before  adding  the  gelatin.  The  gelatin  should  then  be  dissolved  in 
hot  grape  juice  and  thoroughly  stirred  into  the  juice.  These  finings 
can  be  recommended  for  use  before  settling. 

Dried  egg  albumen  at  the  rate  of  4  ounces  to  100  gallons  of  juice 
without  tannin  may  be  used  for  the  late  fining  but  has  not  given  good 
results  before  settling. 

The  best  results  for  early  fining,  before  settling,  were  obtained  by 
the  use  of  Lactocol  or  Casein  at  the  rate  of  from  two  to  six  ounces  per 
100  gallons,  according  to  the  character  of  the  juice.  Lactocol  is  more 
convenient  to  use  as  it  dissolves  easily  in  warm  water.  Casein  has  to 
be  dissolved  with  the  aid  of  sodium  carbonate  or  other  alkali.  Silicate 
of  soda  at  the  rate  of  2  to  4  ounces  per  hundred  gallons  gave  fair  results. 

Whenever  the  juice  does  not  become  bright  by  itself,  fining  is  advis- 
able. Even  though  the  fining  is  not  completely  successful  in  clearing 
the  juice,  its  use  much  facilitates  the  final  filtration. 


*The  juice   may   be   filtered   a  few   hours   after   heating  with   the   finings.     It   will 
usually  remain  bright  after  this  but  will  deposit  cream  of  tartar. 


OUTLINE  OF   RECOMMENDED  METHODS. 

1.  Domestic  Method — 

Separation  of  Juice 

Sulfiting,  Defecation  and  Settling — 24  to  48  hours 

Bottling  and  Sterilizing  for  30  minutes  at  165°  F. 

2.  Industrial  Method — 

Separation  of  Juice 

Sulfitiug,  Defecation  and  Settling — 24  to  48  hours 

Removal  of  Juice  from  Sediment 

(Addition  of  Finings) 

Heating  to  165°  F. 

Settling  for  one  week  to  three  months. 

Removal  of  Juice  from  Sediment 

(Addition  of  Citric  Acid) 

Filtering   (if  necessary) 

Bottling 

Sterilization  at  160°  F  for  twenty  minutes. 

VARIETIES  OF  JUICE. 

Much  variety  in  color  and  flavor  can  be  given  to  Califorman  grape 
juice  by  the  use  of  different  varieties  of  grapes  and  by  modifications 
in  the  methods  of  manufacture. 

The  finest  and  most  highly  flavored  juice  can  be  made  only  from 
thoroughly  mature  grapes,  in  perfect  condition,  of  the  best  varieties. 
However,  any  variety  of  vinefera  grapes,  even  if  not  in  the  best  con- 
dition, such  as  good  table  grape  culls,  if  treated  carefully  as  described, 
will  produce  a  very  acceptable  juice  of  much  higher  quality  than  most 
of  that  which  appears  in  the  market  either  under  a  Californian  or  an 
Eastern  label.  Much  of  the  juice  is  defective  in  flavor  and  appearance 
because  of  overheating  and  over  exposure  to  the  air  or  other  unsuitable 
treatment. 

Where  a  choice  is  possible,  grapes  of  high  acidity  should  be  used. 
This  does  not  mean  unripe  grapes,  for  the  full  delicious  flavor  of  the 
grapes  does  not  develop  until  the  grapes  are  quite  mature.  It 
means  grapes  which  retain  their  acidity  even  when  they  are  ripe.  Any 
grape  which  will  make  good  wine  will  make  good  grape  juice  and  the 
best  for  one  purpose  is  the  best  for  the  other.  An  exception  should  be 
made  of  the  Pierce  and  other  Labrusca  varieties,  which  make  good 
grape  juice  but  are  unsuitable  for  wine. 

Many  Californian  grapes  tend  to  be  very  rich  in  sugar  and  rather 
low  in  acidity.  This  makes  the  juice  more  acceptable  to  some  palates. 
To  others,  it  is  a  defect,  especially  if  the  juice  is  diluted  with  water, 
when  consumed.  Most  juice  can  be  improved  by  the  addition  of  a  little 
citric  acid,  as  already  indicated.  The  excessive  sweetness  of  the  juice 
would  be  remedied  by  diluting  with  water,  but  it  would  seem  more 
advisable  to  allow  the  consumer  to  do  this  to  his  own  taste. 

The  color  of  the  juice  can  be  modified  in  several  ways.  It  may  be 
made  nearly  water  white  or  dark  red.  Many  tints  between  these,  vary- 
ing from  greenish  yellow  to  golden  or  pink,  may  also  be  obtained.  The 
2— CiRlOS 


—  10  — 

lightest  colors  are  obtained  by  moderate  aeration  before  sulfiting  and 
as  little  aeration  as  possible  after.  By  this  means,  juice  without  any 
reddish  tint  can  be  made  even  from  red  grapes.  In  this  case,  the 
aeration  must  be  sufficiently  prolonged  to  destroy  any  color  which  gets 
into  the  juice  during  the  crushing  and  pressing  of  the  skins  and  the 
sulfite  should  be  added  as  soon  as  the  coloring  matter  is  oxidized.  This 
oxidation  is  shown  by  the  change  of  the  pink  color  of  the  juice  to 
brownish  and  the  formation  of  minute  brown  solid  particles  of 
oxidized  coloring  matter. 

Eed  juice  can  be  made  in  three  ways.  One  is  to  use  grapes  with 
colored  juice  such  as  the  Bouschets.  Such  juice  will  be  pink  or  light 
red.  Another  way  is  to  heat  the  crushed  red  grapes  before  the  com- 
plete separation  of  the  juice  and  defecation.  This  may  be  done  by 
heating  all  the  grapes  in  a  boiler  or  by  heating  a  portion  of  separated 
juice  and  pumping  it  on  to  the  skins.  A  temperature  of- 120°  F.  of  the 
whole  mass  is  sufficient  to  extract  the  color  in  several  hours.  At  higher 
temperatures,  the  extraction  is  more  rapid.  This  method  is  not 
advisable,  as  it  exposes  the  hot  juice  too  much  to  the  air,  makes  it  very 
astringent  and  injures  the  flavor.  A  better  method  is  to  separate  and 
defecate  the  juice  as  usual  and  to  color  it  with  a  deep  red  juice  made 
from  the  skins  of  dark  colored  grapes.  This  red  juice  is  made  as 
described  above  after  draining  off  some  of  the  free  run  of  juice. 

In  this  way,  the  fresh  flavor  of  the  juice  is  injured  very  little  by 
the  small  quantity  of  heated  red  juice  added. 

Varieties  of  Grapes.  As  already  indicated^  palatable  grape  juice  can 
be  made  from  any  of  our  ripe  grapes.  For  the  best  results,  however, 
some  care  must  be  exercised  in  the  choice,  blending  and  degree  of  ripe- 
ness of  the  varieties. 

What  is  required  is  full  acidity  and  flavor.  Up  to  a  certain  stage, 
the  riper  the  grapes  the  fuller  the  flavor  but  the  lower  the  acidity. 
Most  of  our  varieties  do  not  attain  their  full  flavor  until  they  have 
reached  a  stage  of  ripeness  representing  at  least  22°  Balling.  For  a 
good  fresh-tasting  juice,  the  acidity  ought  to  be  about  the  equivalent 
of  .7  per  cent  to  .8  per  cent  of  tartaric  acid. 

The  average  composition  of  Californian  grapes,  based  on  seven 
hundred  analyses  of  many  varieties  from  many  sections,  is  23.4°  Balling 
and  .58  per  cent  acid.  These  grapes  were  gathered  as  nearly  as  possible 
when  they  were  at  the  best  stage  for  wine-making.  To  obtain  a  juice 
of  the  composition  desired  for  grape  juice,  most  varieties  would  have 
to  be  gathered  less  ripe  than  this.  Varieties  which  retain  their  acidity 
to  an  advanced  stage  of  ripeness  are  particularly  suitable  for  grape 
juice  as  are  also  varieties  with  a  high  special  flavor. 


—  11  — 


A  list  of  such  varieties,  together  with  some  typical  analyses  is  given 
in  the  following  table : 

SOME   VARIETIES  SUITABLE    FOR  GRAPE   JUICE. 


Variety 

Composition 

Coast    region 

Interior 

Ripe 

Overripe 

Kipe 

Overripe 

Sugar 

Acid 

Sugar 

Acid        Sugar 

Acid 

Sugar 

Acid 

Varieties  with  Special 
Flavors. 
Muscat  of  Alexandria 

21.83 

.74 

27.20 

.54 

Traminer 

25.10 

25.45 
23.96 
24.10 

.38 
.46 
.46 
.41 

Riesling,    Franken 

21.92 
22.15 

.50 
.66 

24.40         .50 

i 

Riesling,  Johannisberg  
Semillon 

21.50 
21.50 

.63 
.68 

25.90 
25.50 
25.50 

26.03 

23.80 
23.24 
25.12 

22.30 
26.90 
26.10 
23.50 

.32 
.37 
.39 

.41 

.45 
.45 
.62 

.43 
.64 
.47 

.56 

Colombar 

Cabernet  Sauvignon 

21.95 
22.00 

20.50 
17.20 
21.50 

21.60 
21.93 
20.20 
20.00 

.77 
.64 

.80 
.99 
.92 

.92 
.80 
1.39 
1.07 

25.34 
24.79 

23.10 
22.60 
25.20 

23.70 
26.50 
23.25 
25.90 

.50 
.44 

.77 
.79 
.86 

.69 
.70 
1.15 
.66 

Means       _ 

22.31 

18.60 
19.60 
22.40 

21.20 

.64 

.61 

.56 

.77 

.65 

Varieties   with  High  Acid. 
Folle  Blanche  

Burger  

West's  White  Prolific  

Varieties  with  High  Acid  and 
Color. 

Bouschet,  Alicante 

Gamai,    Tpintm*ifir 

Gros  Mansenc 

24.35 
21.90 

.88 
.70 

St.  Macaire 

Alicante  Ganzin  

Means 

20.42 
23.20 
21.07 

.98 
.75 

.87 

24.32 
26.50 
24.63 

.80 
.65 
.64 

21.34 
2S-.59 
21.83 

.70 
.64 

.65 

24.42 
28.34 
25.29 

.52 
.39 
.45 

Zinfandel 

Means  of  all  _ 

This  table  shows  that  all  the  highly  flavored  varieties  are  somewhat 
lacking  in  acidity  when  ripe  whether  grown  near  the  coast  or  in  a 
warmer  region.  The  acid  varieties  have  sufficient  acidity  when  grown 
in  the  coast  region  even  when  overripe.  In  the  warmer  regions,  how- 
ever, even  these  varieties  lose  too  much  of  their  acidity  if  allowed  to 
become  overripe..  The  best  quality  would  probably  be  obtained  by 
blending  the  juice  of  highly  flavored  varieties  when  they  were  fully 
ripe  with  acid  varieties  gathered  while  the  acidity  was  still  high.  For 
example:  A  mixture  of  Muscat  showing  25°  Bal.  of  sugar  and  .55 
per  cent  acidity  with  West's  White  Prolific,  showing  20°  Bal.  of  sugar 
and  .95  per  cent  acidity  would  give  a  juice  of  22.5°  Bal.  and  .75  per 
cent  acidity.  The  Prolific  would  supply  the  acid  and  the  fully  ripe 
Muscat  the  flavor. 

A  series  of  tests  of  the  sugar  and  the  acid  in  Muscat  grapes  at  various 
stages  of  ripeness  gives  an  example  of  the  changes  which  take  place  in 
the  ratio  between  sugar  and  acidity. 


—  12  — 

COMPOSITION   OF    MUSCAT   GRAPES  AT  VARIOUS  STAGES   OF    RIPENESS. 


ill 


Edible - 21.8 

f  25.5 

Eipe  -i  26.2 

I  26.8 
[27.2 

Overripe  -i  29.1 

133.2 


Acidity 
Sugar  (as 

iBal.*)   tartaric) 

.72 

.63 
.62 
.50 
.54 
.54 
.70 


"With  a  sugar  content  of  21.8°  Bal.,  the  grapes  were  edible  and  the 
acid  sufficiently  high  but  the  full  Muscat  flavor  had  not  developed. 
When  the  sugar  had  risen  to  25.5°  Bal.  the  flavor  was  fully  developed 
but  the  acidity  was  a  little  low.  This  was  the  best  stage  to  gather  these 
grapes  for  grape  juice.  As  they  got  riper,  the  acidity  fell  until  at  full 
ripeness  (the  stage  for  raisin  making),  nearly  one  third  of  the  acidity 
was  lost.  The  apparent  increase  of  acidity  with  overripeness  does  not 
indicate  a  gain  of  acid  but  simply  concentration  due  to  evaporation  of 
water. 

As  a  general  rule,  the  grapes  for  flavoring  should  be  gathered  when 
the  sugar  reaches  23°  to  25°  Balling  and  the  grapes  for  acidity  when 
it  reaches  19°  to  21°  Bal. 

Eastern  Varieties.  Grape  juice  made  in  New  York  and  other  eastern 
states  is  sold  in  large  quantities  even  in  California.  Various  samples 
show  variations  in  quality,  but  they  all  differ  from  the  Californian 
juices  in  their  higher  acidity  and  their  strong  Labrusea  flavor.  We 
can  obtain  the  acidity  by  gathering  our  grapes  with  the  low  percentage 
of  sugar  customary  in  the  East.  The  Labrusea  flavor  we  can  obtain 
only  by  growing  the  Eastern  grapes.  These  grapes,  Concord.  Isabella, 
Catawba,  etc.,  do  very  well  in  the  cooler  parts  of  California,  bearing] 
larger  crops  of  sweeter  grapes  than  they  do  in  most  Eastern  vineyards. 
The  Pierce,  an  improved  Isabella,  would  probably  be  very  suitable  for| 
producing  a  Californian  grape  juice  of  the  Eastern  type. 

Which  would  be  more  profitable,  to  produce  grape  juice  from 
Labrusea  varieties,  thus  taking  advantage  of  a  market  already  estab-l 
lished,  or  to  develop  the  market  for  juice  made  from  our  Californian 
varieties,  experience  alone  can  determine.  There  can  be  little  doubt 
that  both  kinds  of  grape  juice  can  be  produced  here  profitably  when 
the  manufacturers  adopt  methods  which  will  insure  the*  conservation! 
of  the  good  qualities  of  our  grapes. 


Makers 

Syracuse,  N   v 


288520 


r  T  ! 


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